Marine shipping involves one important aspect to consider--fire protection on board. Big fire extinguisher tanks are stored on board for emergency. Knowing the liquid level in tanks is what Ultrasonic Liquid Level Indicator specializes, allowing users to detect liquid level in tanks without opening them. It is extremely convenient and safe to use, which is necessary for shipping. The material of measurable liquid containers can be made of various kinds of materials like metal, glass or unfoamed plastics. Under ordinary conditions, the maximum wall thickness of measurable containers is 30mm.